p5pRT
commented
24 years ago From pbdb_test@rfi.net
For some reason\, Perl accepts a while loop with an empty conditional. while ( ) { print "TRUE"; sleep 1; } results in a big list of TRUEs. This is odd in several ways:
1) Everything else (until\, if\, unless...) is a syntax error with an empty condition. 2) The empty condition of a while loop is TRUE! If anything I would expect false. 3) There's no warning.
At minimum there should be a warning\, at best it should be made a syntax error.
This looks like a documentation problem.
Here's another intersting problem:
do { print "TRUE"; sleep 1 } while (); This produces one iteration of TRUE.
do { print "TRUE"; sleep 1 } until (); This produces an infinite loop.
Again\, the oddness: 1) Unlike with while () {...}\, the null condition is false! 2) Again\, no warning.
IMHO do {...} while () and do {...} until () should both be syntax errors\, or at least warnings.
Unless there's a backwards compatibility issue\, all instances of an empty conditional should probably be a syntax error. I can't think of any time when it would be useful.
If I'm feeling brave I'll submit a patch.
PS This problem occurs under 5.005_03 and 5.005_62
Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration: Platform: osname=macOS\, osvers=2.2.7\, archname=i686-linux uname='linux athens 2.2.7 #2 smp mon may 10 23:17:01 edt 1999 i686 unknown ' hint=recommended\, useposix=true\, d_sigaction=define usethreads=undef useperlio=undef d_sfio=undef Compiler: cc='gcc'\, optimize='-O6'\, gccversion=egcs-2.91.66 19990314 (egcs-1.1.2 release) cppflags='-Dbool=char -DHAS_BOOL -I/usr/local/include' ccflags ='-Dbool=char -DHAS_BOOL -I/usr/local/include' stdchar='char'\, d_stdstdio=undef\, usevfork=false intsize=4\, longsize=4\, ptrsize=4\, doublesize=8 d_longlong=define\, longlongsize=8\, d_longdbl=define\, longdblsize=12 alignbytes=4\, usemymalloc=y\, prototype=define Linker and Libraries: ld='gcc'\, ldflags =' -L/usr/local/lib' libpth=/usr/local/lib /lib /usr/lib libs=-lnsl -lndbm -lgdbm -ldbm -ldb -ldl -lm -lc -lposix -lcrypt libc=\, so=so\, useshrplib=false\, libperl=libperl.a Dynamic Linking: dlsrc=dl_dlopen.xs\, dlext=so\, d_dlsymun=undef\, ccdlflags='-rdynamic' cccdlflags='-fpic'\, lddlflags='-shared -L/usr/local/lib'
Characteristics of this binary (from libperl): Built under linux Compiled at Jul 29 1999 00:29:00 %ENV: PERL5LIB="/home/schwern/lib/perl5/site_perl/5.005:/web/sites/test/mp" @INC: /home/schwern/lib/perl5/site_perl/5.005/i686-linux /home/schwern/lib/perl5/site_perl/5.005 /web/sites/test/mp /usr/lib/perl5/i686-linux /usr/lib/perl5 /usr/lib/perl5/site_perl/5.005/i686-linux /usr/lib/perl5/site_perl/5.005 .
Summary of my perl5 (revision 5.0 version 5 subversion 62) configuration: Platform: osname=linux\, osvers=2.2.10\, archname=i686-linux uname='linux athens 2.2.10 #3 smp mon aug 2 16:48:09 edt 1999 i686 unknown ' config_args='' hint=recommended\, useposix=true\, d_sigaction=define usethreads=undef useperlio=undef d_sfio=undef use64bits=undef usemultiplicity=undef Compiler: cc='cc'\, optimize='-g'\, gccversion=2.95.2 19990906 (prerelease) cppflags='-Dbool=char -DHAS_BOOL -DDEBUGGING -I/usr/local/include -DDEBUGGING_OPS -DDEBUGGING_MSTATS -fno-strict-aliasing' ccflags ='-Dbool=char -DHAS_BOOL -DDEBUGGING -I/usr/local/include -DDEBUGGING_OPS -DDEBUGGING_MSTATS -fno-strict-aliasing' stdchar='char'\, d_stdstdio=define\, usevfork=false intsize=4\, longsize=4\, ptrsize=4\, doublesize=8 d_longlong=define\, longlongsize=8\, d_longdbl=define\, longdblsize=12 alignbytes=4\, usemymalloc=y\, prototype=define Linker and Libraries: ld='cc'\, ldflags =' -L/usr/local/lib' libpth=/usr/local/lib /lib /usr/lib libs=-lnsl -lndbm -lgdbm -ldbm -ldb -ldl -lm -lc -lposix -lcrypt libc=/lib/libc-2.1.2.so\, so=so\, useshrplib=false\, libperl=libperl.a Dynamic Linking: dlsrc=dl_dlopen.xs\, dlext=so\, d_dlsymun=undef\, ccdlflags='-rdynamic' cccdlflags='-fpic'\, lddlflags='-shared -L/usr/local/lib'
Characteristics of this binary (from libperl): Compile-time options: DEBUGGING Built under linux Compiled at Oct 16 1999 16:16:24 %ENV: PERL5LIB="/home/schwern/lib/perl5/site_perl/5.005:/web/sites/test/mp" @INC: /home/schwern/lib/perl5/site_perl/5.005/i686-linux /home/schwern/lib/perl5/site_perl/5.005 /web/sites/test/mp /usr/local/perl5.005_62/lib/5.00562/i686-linux /usr/local/perl5.005_62/lib/5.00562 /usr/local/perl5.005_62/lib/site_perl/5.00562/i686-linux /usr/local/perl5.005_62/lib/site_perl .
--
Michael G Schwern schwern@pobox.com http://www.pobox.com/~schwern /(?:(?:(1)[.-]?)?\(?(\d{3})\)?[.-]?)?(\d{3})[.-]?(\d{4})(x\d+)?/i
Migrated from rt.perl.org#2115 (status was 'resolved')
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